[Qemu-devel] ARM: Registering memory for KVM

[Christoffer Dall]

I am bringing changes from my implementation of KVM for ARM into the
upstream version of QEMU and trying to do things right.

My concern is how handle MMIO mapped device registration with KVM. In
kvm_set_phys_mem(...) it's required that the flags are not >=
IO_MEM_UNASSIGNED. However, for most of the devices, for instance
connected to the integrator board, the cpu_register_physical_memory
(called from hw/sysbus.c) uses dev->mmio[n].iofunc as argument for
phys_offset.

As far as I can understand, this value will always result in flags >=
IO_MEM_UNASSIGNED, since the iofunc value comes from
cpu_register_io_memory(...).

Without fully understanding the different uses of phys_offset, I
gather that my choices are these:
 1. Change the call to cpu_register_physical_memory in hw/sysbus.c
when KVM is enabled
 2. Change the initialization of every device (seems very invasive)
 3. Change kvm_set_phys_mem to deal specifically with ARM (seems like
something more general for other architectures should be done).

I have tried looking at the PPC and x86 implementations, but it seems
that the MMIO devices are not created with dedicated io zones. If
anyone can explain this difference between the way it's done on ARM
and either PPC or x86, it would for sure clear things up for me.

Thanks!

Best regards,
Christoffer Dall